Noncontact Evaluation Method for Autonomic Nervous System Activity during Exercise Using RGB Camera.

For efficient exercise, motor functions, heart rate, oxygen uptake (which are controlled by autonomic nervous system activity), heat acclimation-related functions, such as sweating, and thermoregulation must work properly during exercise. In this research, a noncontact method of measuring capillary contraction and dilation, one of the autonomic nervous system activities, using only a commercial web camera was developed. The absorption rate by haemoglobin in blood differs for each wavelength of light. When the capillaries in the face contract or dilate, the colour component of the light reflected from the face changes. The focus of this study was on the changes in the green and blue values of the face image. Green light reaches the dermis, where capillaries are located, while blue light reaches only the epidermis. The G/B ratio, the green value divided by the blue value, shows the changes in capillary contraction and dilation. An experiment was conducted to validate the G/B ratio method. Ten subjects (23 ± 1.6 years of age) participated in the experiment, and face movement and heart rate were measured during an aerobic bike exercise test. The results showed that, when the heart rate increased, the G/B ratio decreased immediately after the start of exercise. After the exercise stopped, the heart rate decreased immediately, and the G/B ratio increased. The G/B ratio revealed that the sympathetic nervous system became dominant during exercise, causing facial capillaries to dilate, and that the parasympathetic nervous system became dominant after exercise, causing facial capillaries to constrict.

Bending Angle Sensor Based on Double-Layer Capacitance Suitable for Human Joint.

Goal: To develop bending angle sensors based on double-layer capacitance for monitoring joint angles during cycling exercises. Methods: We develop a bending angle sensor based on double-layer capacitive and conducted three stretching, bending, and cycling tests to evaluate its validity. Results: We demonstrate that the bending angle sensor based on double-layer capacitance minimizes the change in the capacitance difference in the stretching test. The hysteresis and root mean square error (RMSE) compared with the optical motion capture show hysteresis: 8.0% RMSE and 3.1° in the bending test. Moreover, a cycling experiment for human joint angle measurements confirm the changes in accuracy. The RMSEs ranged from 4.7° to 7.0°, even when a human wears leggings fixed with the developed bending-angle sensor in the cycling test. Conclusion: The developed bending angle sensor provides a practical application of the quantitative and observational evaluation tool for knee joint angles.

Attenuated spontaneous postural sway enhances diastolic blood pressure during quiet standing.

PURPOSE: Spontaneous postural sway during quiet standing has been considered a simple output error of postural control. However, as postural sway and inherent body orientation evoke compensatory activity of the plantar flexors, they might contribute to blood circulation under gravitational stress via the muscle pump. Hence, the present study employed an external support device to attenuate the plantar flexor activity in supported standing (SS), to experimentally identify its physiological impact on blood circulation. METHODS: Eight healthy young subjects performed two 5-min quiet standing trials (i.e., normal standing (NS) and SS), and the beat-to-beat interval (RRI) and blood pressure (BP) were compared between trials. We confirmed that postural sway and corresponding plantar flexor activity, quantified by the anteroposterior displacement of the foot center of pressure and lower back position with respect to the wall, and by the amplitude of electromyography and mechanomyography, respectively, were attenuated in SS, while mean body orientation angle and relative position of the BP sensor were comparable to NS. RESULTS: The 5-min averages of diastolic BP and mean arterial pressure during SS were significantly higher than during NS, while RRI and systolic BP did not change. These could be interpreted as an increase in peripheral vascular resistance; meanwhile, in NS, this effect was replaced by the muscle pump of the plantar flexors. CONCLUSION: The muscle contractions related to spontaneous postural sway and body orientation produce substantial physiological impact on blood circulation during quiet standing.

Signal source estimation inside the human heart during ventricular activation using switching voltage divider.

A novel signal source estimation method using switching voltage divider technology was developed in our previous works. The aim of this method is to reduce the number of electrodes required for signal source estimation. Using this method, voltage and position information about the signal source inside the human body can be obtained simultaneously. The purpose of this paper is to estimate the changes in the signal source location according to ventricular activation. One healthy male (31 years old) participated in an ECG measurement experiment that utilized switching voltage divider technology. Nine signal electrodes and one ground electrode were attached to the participant's body surface, and the electrocardiogram was measured with the patient seated. The signal sources for early QRS, mid QRS, and late QRS, were estimated. Results suggest that changes in the signal source location could be estimated during ventricular activation.

Evaluation of lower leg swelling using EMG measured with voltage divider.

The purpose of this study is to evaluate the lower leg swelling using EMG measured with our new voltage divider technology, by which the internal impedance of lower leg can be estimated. The amplitude of EMG measured without voltage divider was compared to it with voltage divider. Eleven healthy subjects (24.3±5.1 y.o.) participated in this study. Six female (swelling group) were asked to work at desk for six hours, and five male (control group) were asked to work a regular day. The internal impedance was calculated and calf circumference was measured before and after desk work. Results show that internal impedance in swelling group significantly decreased with increase in calf circumference, and our new evaluation method was proved to be effective for the evaluation of lower leg swelling.

Measurement of swallowing using flexible polymer sensor.

We proposed a new method to measure swallowing in this study. A flexible polymer sensor was used to measure human swallowing. Electromyogram (EMG) of suprahyoid muscles were measured as a reference of swallowing. We also developed a measurement system for the flexible polymer sensor, which consists of two measurement circuits; the 1(st) one measures the voltage of flexible polymer sensor, and the 2(nd) one EMG of suprahyoid muscles. We conducted measurement experiments focused on human swallowing to confirm the ability of this sensor. At the experiment one subject was asked to sit in three different postures and to drink a cup of water. Results show that human swallowing can be detected by this flexible polymer sensor.